This script is possibly vulnerable to file inclusion attacks.
It seems that this script includes a file which name is determined using user-supplied data. This data is not properly validated before being passed to the include function.
It is possible for a remote attacker to include a file from local or remote resources and/or execute arbitrary script code with the privileges of the webserver.
Edit the source code to ensure that input is properly validated. Where is possible, it is recommended to make a list of accepted filenames and restrict the input to that list.
For PHP, the option allow_url_fopen would normally allow a programmer to open, include or otherwise use a remote file using a URL rather than a local file path. It is recommended to disable this option from php.ini.
PHP - Using remote files
OWASP PHP Top 5
Remote file inclusion